Constant tension winding



Patented Sept. 16, 1952 CONSTANT TENSION WINDING Robert P. Lathrop, Chevy Chase, Md., assignor to .E.I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Application September 20, 1950, Serial No. 185,837

1 v -This invention relates to an apparatus and method for-winding yarn-at constant tension and, in particular, relates to an apparatus for converting a pirn wind-up to constant tension spool windeup.

Lsequently creeled and drawn several times their original length and finally wound onto a shipping package. In some cases where special twist is required, additional windings are necessary.

, During winding on a bobbin or pirn the tension on the materialjbeing wound usually changes progressively as the bobbin fills up and the diameter increases.v Particularly in do-wntwister pirn wind-up, low uniform winding tensions are incompatible with large ratios of inside to outside package diameters'and high feed speeds. The higher the feed speed, the greater .will be the tension increase in winding the outside as compared with the inside of the package unless the over-all winding tension is greatly increased by greater spindle speed, other dimensions remaining constant. Constant tension winding is necessary to avoid stretching and to produce a uniform. package of yarn having uniform physical propertiesthroughout the package.

In the preparation of some synthetic yarns it has been found advantageous to wind the as-spun yarn on a spool-type cylindrical pirn by means of a downtwister yarn take-up. When spinning certain types of yarns at speeds up to 300 yds./min., the downtwister type take-up is quite satisfactory since the tension can be made to remain suitably low and fairly uniform throughout the winding. However, when higher spindowntwister. take-up to a traverse bobbinwinder 71Claims. (01. 242-45) which will wind yarn, film, ribbons, etc. at constant tension. It is an object of this invention to provide a means for winding yarn under constant tension. It is a particular object to provide a means for winding yarn at high speeds at low uniform tension. It is still a further object to provide for the preparation of much larger packages of yarn with no major change in design of the take-up. Another object is to provide a spool winder which maintains constant winding tension through controlled torque applied to the spool as opposed to surface drives and variable speed drives. Other objects will become obvious from the description of the invention which follows.

The objects of this invention are accomplished by the provisionof an adapter assembly which fits snugly over a spindle of the type commonly used on a downtwister type take-up. The

adapter assembly comprises aninner shell which supports a tubular outer shell on ball bearings, the inner shell being driven by the constant speed spindle and containing a magnetic clutch. which induces eddy currents in a drag member; located within its field, attached to the outer shell, whereby the outer shell is caused to'rotate. By proper choice of the spindle speed it isfpossible to wind filaments, yarns, and the like on aspool supported by the adapter assembly at high speeds under relatively constant low winding tension. In order tofacilitate the description, reference will be had to the appended drawings which are given for illusti-ativepurposes only and of which: Figure 1 is a cross-section showing the general arrangement of the elements of one embodiment of this invention;

Figure 2 is a sectional plan view of the magnet assembly taken on line 2-2 of Figure 1; and

Figure 3 is a cross-sectional view of another embodiment of the invention.

In Figure 1, the inner shell 2 fits snugly over the spindle I and extends into flange 6 which contains two holes 50 and 5|, as shown, by means of which the inner shell is firmly attached to the driving means. The outer shell 3 is concentric with inner shell 2 and fits over said inner shell,

being spaced from it and freely rotatable thereon by means of ball bearings 4. The bearings 4 are preferably positioned near the top and near the base of inner shell 2 as shown. The upper hearing is held in place by means of a snap ring 5 which fits into a circular recess in the inner surface of the outer shell 3. The snap ring 5 supports the outer shell 3 above flange 6 so that the ring is freely rotatable. The magnet element is positioned at the top of the inner shell 2 by means of cap screw is and bevel nut H. The magnet element comprises magnet holder 1 and permanent magnets 3 positioned therein as shown in Figure 2. The magnet element rests on the backing plate is which positions the magnet with respect to the bearing 4. The backing .plate 9 also closes the l'owerimagnetic field. The magnet may be one unit of two poles or it may consist of several units each having two poles. It maybe a permanent or an electromagnet.

The drag member l3 comprises an aluminum disc and is suitably attached tothe end of bolt I2. The bolt I2 is positioned'b-y' the-internally threaded support l5 which is fixedrtothe top of the outer shell 3 by screws H3. The "distance of drag member is from magnet .8 :can be-varied by means of bolt l2. The position of the drag member I3 is maintained during operation by means of the lock nut I 3 and bolt l2. The cap [6 shown in the figure is not essentialiand serves merely to cover the headset-screws [8 in order to eliminateany-possibility of a running length of yarn snaggingthereon. 'The holes l9 and 2e above the drag member are provided to allow some cooling of the drag member i3 if required. When the outer shell 3 rotates, particularly at high speeds, a flow of air is induced into holes and out of holes H3. The pin H, at the base, is stationary and cooperates with a'longitudinal slot "in the bobbin or spool to prevent'any movement of the bobbin or spool relative to the outer shell 3.

In practice when it is desired to change from pirn wind-up on a dovvntwister machine to a high speed, constant tension wind-up, it is necessary only-to fit :the adapter and .its essential parts, cas shown .in .Figuresuhand 3,. over the spindle and remove .the .traversingrring and traveler from the. traversingdring rail, replacing :them with a suitablestraversing guide. The take- .upxspool, bobbin .ora idoublefianged pirn, as

.shownxby dottedllincs .52, to bezused-is then fitted :over theoutsideof .the outershell 3 of thecomplete. adapter assembly. The take-up spool rides onrthe flange 53:at thebaseof outer shell 3. The-'positivelydriven spindle l rotates the .innersshelll2flandthe attached magnet 8. The V rotation ;of "magnet 8 :induces eddy current flow fiirdrag member t3, thereby effecting rotation oirthe drag member andthe outershell 3 and the :spool attached thereto;

When yarn .is not being-wound on the spool, the speed of'the V the drag member which is'proportional to the difference'inrotational speeds of the spindle and :thei-spool, this difierence being :knownas the slip -By choosing the proper irelation between the spindle speed'and yarnieed speed, the slip can be made. nearly proportional :to: the :package diameter. 'Inthis manner, the'torque'is made nearly proportional to the package diameter and the winding tension remains essentially con- "stant; The magnitude of tension on the yarn being wound is controllable by changing'the "strength of the field intercepting the drag memher. This canbe done either by varying the air gap between the magnetandthe dragmem- "-ber orby shunting the magnet.

In Figure 3, another embodiment of the invention, comprising a different magnetic arrangement, is shown. The inner shell 2 supports an extension 22 which narrows into stud 32. The inner shell extension 22 supports the upper bearing 23 together with the adapter 2|. The bearing 23 is held in place by means of snap'ring 24. The adapter 2l' is he1d'jin place by thesnap ring 5 which also supports the outer shell 3above flange 6 so that is freely rotatable. The magnet 25 comprises a disc and shoulder extension which fit over the stud 32. The magnet 26 is secured in its position by nut 21 and contactv with. theouter shell assembly is preventedby meansiof the spacer 25. The magnet has positive andnegative poles at opposite edges ofthe. .discandrotation of the magnet induces eddy current now in the cylindrical drag member 28 positioned in the upper part of the outer shell 3 by cap 29, pin. Bil and set screw 31. In normal use little heat visdeveloped by this eddy current. device .and consequently, the airvents shown in the apparatus of Figure '1 are not provided.

The intensity of the magnetic field intercepting the drag member 23 and the corresponding tension on the yarn being wound may be decreased by shunting the magnet. 26. The magnet may be shunted readily and simply by placing an ordinary washer on the uppersurface.

.theelectromagnet. This permits adjustment oftension withease.

Any magnetic material may be used in the magnet element, although the stronger and more permanent Alnico types are preferred. Naturally, both positive and negative poles must be at the surface near the drag member, so that eddy current flow is induced in the. dragmember. The .drag'member should be made from .a

v metal having low electrical resistance, preferably aluminum, but'it may bemade of other metals, such "as copper- It has bEBllTfOlIIldiiIlllSlHE the winding apis 'necessary'tochoose the proper spindle speed.

"Since'thespindle speed and the yarnfeed speed are maintained constant throughout the winding,the slip will increase as the package radius increases. The winding device of this invention operates on a practically straight line relation between slip and torque. By a proper choice of spindle speed the magnet imparts a torque to the drag member which is inversely proportional to the absolute speedof the drag plate (inthe speed range encountered inpractice). Since this arrangement causes the torque to increase in direct ratio'with the package radius, it is possible to wind yarn at constant 'linearfeed speeds with nearly constant winding' tension. The choice of the proper spindle speed necessary to wind a yarn'at constant tension throughout the winding of a package of "yarn is dictated by the 'following equation:

- imam SP- 0102 wherein SP-denotes the spindleaspeedin R. P; M.,

'F; denotes :the deed .speedjnjthe .linearuunits per minute, and C1 and C2 denote the initial and final circumference of the package in the same linear units as F, and C2 does not exceed 401. It has been found that if considerably higher spindle speeds than determined by the equation are used, the tension on the yarn, while at a higher level, decreases constantly throughout the winding of the package. On the other hand, if too low a spindle speed is used, the tension, at a lower level, will mount continually through-- out the winding of the package. By using the spindle speed determined by this equation, it has been found that winding at constant tension can be achieved irrespective of yarn feed speed as long as the final package radius does not exceed four times the initial radius. At this point the equation begins to fall seriously and the spindle speed and its relation to yarn feed speed must be determined experimentally.

The apparatus of this invention has many advantages. It affords an easy means for converting twister take-up to a higher speed, uniform tension take-up (which may be operated at any predetermined tension level). It economically combines the good points of twister and spool take-ups while eliminating the disadvantages of surface driven packages or elaborate variable speed drives. Since several elements of twister apparatus, such as travelers, traveler rings, rotating balloons, balloon suppressors, and separators, are eliminated, the weight of the traversing mechanism is minimized. It provides for winding much larger packages of yarn on the same center distance with no major change in design of the take-up. The problem of yarn protection in the wind-up through applying finish is simplified since ceramic traversing guides can be used instead of metal travelers and rings. The winding of transfer tails on yarn packages also becomes much simpler. In addition, it permits the winding of water-laden yarn, which presents severe ring maintenance problems with a twister take-up.

Any departure from the procedure described herein which conforms to the principles of the invention is intended to be included within the scope of the claims below.

I claim:

1. A device for winding a filament under constant tension comprising a spindle driven at constant speed; an inner shell mounted on and driven by said spindle; bearings at the top and at the base of said inner shell; mounted on said bearings an outer shell freely rotatable in respect to said inner shell; mounted at the top of and within said inner shell a magnet; mounted at the top of and within said outer shell a drag member located within the field of said magnet and affected thereby to rotate said outer shell upon rotation of said magnet; and at the bottom of said outer shell a flange to support a take-up unit on which said filament is wound.

2. Apparatus in accordance with claim 1 in which the said drag member is adjustably mounted so that the distance between the said drag member and said magnet may be varied.

3. Apparatus in accordance with claim 1 in which the said drag member is composed of a metal of low electrical resistance.

4. Apparatus in accordance with claim 1 in which the said outer shell contains air vents in the vicinity of said drag member.

5. A wind-up device comprising a spindle driven at constant speed; an inner shell mounted on and driven by said spindle; bearings at the top and at the base of said inner shell; mounted on said bearings an outer shell freely rotatable in respect to said inner shell; mounted at the top of and within said inner shell a magnet element comprising a magnet holder and positioned therein a magnet; mounted at the top of and within said outer shell a drag member comprising a disc of a material of low electrical resistance located Within the field of the said magnet, the rotation of which induces eddy current flow in said drag member thereby effecting rotation of said drag member and said outer shell.

6'. Apparatus in accordance with claim 5 in which the outer shell contains air vents in the vicinity of said drag member.

7. Apparatus in accordance with claim 5 in which the outer shell has a flange at the bottom end thereof to support a take-up unit.

ROBERT P. LATHROP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

